I accidentally stole the female lead's first love ASFLFL

The almost college student is trapped in the body of the 5-year-old daughter of a destitute baron.
Her goal is to give this family what she couldn't to hers, and try to live as Theresse Halligan.
She thought it would suit her, but she did not imagine she was in the world of an old fantasy web novel!
Well, she wasn't even mentioned in the novel, and she had better things to worry about than the characters in a romantic love story.
As long as she, her family, and little Gilles were okay, nothing could be that bad.
But little Gilles, Why do you bring so much trouble?